Network Direct Attached Storage

Network Direct Attached Storage (NDAS) is a proprietary storage area network system, originally marketed by the company Ximeta, for connecting external digital storage devices such as hard-disks, flash memory and tape drives via the Ethernet family of computer networks. Unlike other more common forms of networked storage, NDAS does not use TCP/IP to communicate over the network. Instead a Lean Packet Exchange (LPX) protocol is used.^[1] NDAS also supports some limited RAID functions such as aggregation and mirroring.

History

In 2001, Han-gyoo Kim of Korea and Zhe Khi Pak of Russia applied for a US patent on a "network-attached disk".^[2] By 2002 the first NetDisk (up to 80 GB) was marketed as a low cost alternative to full computer based network storage options. The Ximeta company was founded in 2003.^[3] In 2004 Kim applied for a patent to allow multiple clients write access to the shared block storage device.^[4] By 2006, sizes up to 500 GB were supported.^[5] In 2008 an NDAS device called "ShareDisk Gigabit" created by Co-World Cs in Germany briefly claimed the title of world's fastest network storage device.^[6]

In 2011 IOCELL Networks announced ownership of the NDAS system and NetDisk patents.^[7] The following year, IOCELL revived Linux client support for NDAS—which Ximeta had "temporarily suspended" in September 2009^[8]—by releasing the drivers under the terms of the GNU General Public License (GPL) as the open-source "ndas4linux" project.^[9]

Benefits

• Hardware is typically easy to set up and use, particularly when a unit is purchased with a disk installed.
• The disk drive can be used via multiple interfaces (typically eSATA, USB or Ethernet) though not concurrently: USB and eSATA allow access by only one host.
• The disks do not require special formatting so they can be treated as external disks on a wide variety of computers.
• Performance (speed vs. cost) is claimed to be better than similarly priced storage devices.
• Devices are isolated from external network discovery since the protocol is not visible through a router.

Drawbacks

Linux Driver Project Code - chunk of GPL code from the NDAS driver

• The LPX Protocol is not routable, thus limiting access to one local area network.
• Some firewall programs block the LPX protocol by default. It uses EtherType value 0x88AD.
• Drivers required to operate NDAS devices over a network are not shipped with operating systems. The devices are usually accompanied with client driver software for Microsoft Windows operating systems.
• Drivers for Linux-based operating systems (Linux distributions such as Fedora, Ubuntu or Debian) were originally available only from the manufacturer.^[10]

See also

A similar protocol is ATA over Ethernet.